20050811, 12:11  #1 
Nov 2003
2·1,811 Posts 
A minor bug in PRP24.14
I'm testing the latest PRP24.14 and I found a minor bug.
On startup when the output file is created (to write PRPs) the sieve limit is truncated to lower 32 bits. For example, the first line of my input file is: 837001000000:M:0:2:258 but the output file reads 3777344576:M:1:2:258 and Mod(837001000000, 2^32)=3777344576. This is not important but I wonder how reliable is the PRP testing part. Last year there was a bug there so serious testing is required. OTOH, that's not so easy when new PRP versions are being released almost every month. So far I only tested 17 known k*2^n1 primes and all were successfully detected. 
20050829, 14:46  #2 
May 2005
2^{2}·11·37 Posts 
Have you tested 24.14 some more? I wonder if there is a possibility for PRP to "miss" a prime and what would be the probability of such event...
I am right now at ~110k with 736320585 and I am looking for a way (other than newpgen) to speed it up  PRP is faster than LLR  the question is: how reliable it is? 
20050829, 15:14  #3 
Nov 2003
2·1,811 Posts 
I did more tests on 24.14 but nothing substantial, just about 20 primes k*2^n1, one half k<300 and the other "15k" like k's (10^810^9), n in the 200300k range, and all were correctly found to be PRPs. I stopped tests because I found that on my PentiumM laptop PRP24.14 performs almost the same like the latest LLR. Maybe it's faster on P4. To answer your question, with a high probability the PRP test part is bugfree because no bugs were reported since last year. But it's impossible to be certain until we have a stable version and more people interested in testing it.
BTW, you can go straight to n=200k, the small guys cannot be reported to Top5000 and the probability to find a SophieGermain by chance at n=100k is miniscule. If you are interested in SG you have to sieve specifically for SG (or "lucky minus"), such options are available in NewPGen. 
20050829, 20:28  #4 
May 2005
2^{2}·11·37 Posts 
I'm planning to make it a comprehensive search from 0 to 1M

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